Sivriss, Nightmare Speaker

{T}, Sacrifice another creature or an artifact: For each opponent, you mill a card, then return that card from your graveyard to your hand unless that player pays 3 life. (To mill a card, put the top card of your library into your graveyard.)
Choose a Background (You can have a Background as a second commander.)

Death Mutation

Destroy target nonblack creature. It can't be regenerated. Create X 1/1 green Saproling creature tokens, where X is that creature's mana value.

Binding the Old Gods

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Destroy target nonland permanent an opponent controls.
II — Search your library for a Forest card, put it onto the battlefield tapped, then shuffle.
III — Creatures you control gain deathtouch until end of turn.

Compy Swarm

At the beginning of your end step, if a creature died this turn, create a tapped token that's a copy of Compy Swarm.

Daemogoth Woe-Eater

At the beginning of your upkeep, sacrifice a creature.
When you sacrifice Daemogoth Woe-Eater, each opponent discards a card, you draw a card, and you gain 2 life.

Deathrite Shaman

{T}: Exile target land card from a graveyard. Add one mana of any color.
{B}, {T}: Exile target instant or sorcery card from a graveyard. Each opponent loses 2 life.
{G}, {T}: Exile target creature card from a graveyard. You gain 2 life.

Cloakwood Hermit

Commander creatures you own have "At the beginning of your end step, if a creature card was put into your graveyard from anywhere this turn, create two tapped 1/1 green Squirrel creature tokens."

Akawalli, the Seething Tower

Descend 4 — As long as there are four or more permanent cards in your graveyard, Akawalli, the Seething Tower gets +2/+2 and has trample.
Descend 8 — As long as there are eight or more permanent cards in your graveyard, Akawalli gets an additional +2/+2 and can't be blocked by more than one creature.

Chatterfang, Squirrel General

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
If one or more tokens would be created under your control, those tokens plus that many 1/1 green Squirrel creature tokens are created instead.
{B}, Sacrifice X Squirrels: Target creature gets +X/-X until end of turn.

Brood Butcher

Devoid (This card has no color.)
When Brood Butcher enters, create a 1/1 colorless Eldrazi Scion creature token. It has "Sacrifice this creature: Add {C}."
{B}{G}, Sacrifice a creature: Target creature gets -2/-2 until end of turn.

Daemogoth Titan

Whenever Daemogoth Titan attacks or blocks, sacrifice a creature.

Culling Ritual

Destroy each nonland permanent with mana value 2 or less. Add {B} or {G} for each permanent destroyed this way.

Drey Keeper

When Drey Keeper enters, create two 1/1 green Squirrel creature tokens.
{3}{B}: Squirrels you control get +1/+0 and gain menace until end of turn.

Deathbloom Ritualist

{T}: Add X mana of any one color, where X is the number of creature cards in your graveyard.

Catacomb Sifter

Devoid (This card has no color.)
When Catacomb Sifter enters, create a 1/1 colorless Eldrazi Scion creature token. It has "Sacrifice this creature: Add {C}."
Whenever another creature you control dies, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Back for More

Return target creature card from your graveyard to the battlefield. When you do, it fights up to one target creature you don't control. (Each deals damage equal to its power to the other.)

Acolyte of Affliction

When Acolyte of Affliction enters, mill two cards, then you may return a permanent card from your graveyard to your hand.

Diregraf Rebirth

This spell costs {1} less to cast for each creature that died this turn.
Return target creature card from your graveyard to the battlefield.
Flashback {5}{B}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Beledros Witherbloom

Flying
At the beginning of each upkeep, create a 1/1 black and green Pest creature token with "When this creature dies, you gain 1 life."
Pay 10 life: Untap all lands you control. Activate only once each turn.

Deathreap Ritual

Morbid — At the beginning of each end step, if a creature died this turn, you may draw a card.